Right now only profession of Small Guns and Big Guns crafter requires three skills: SG/BG, Science and Repair. Combat skill is obvious here, Science - well, you need to make gunpowder, metal parts and alloys somehow, so it seems fine. But Repair?
Armorer profession requires only Repair skill at high level (180% for 3rd), and it also allows to fix stuff easily. 120% repair, required for 3rd level of SG/BG doesn't allow you to fix anything without high possibilty of failure. So I suggest to remove this skill from requirements for those two professions.
+ more preciousss skill points to put elsewhere
+ less crafting alts
+ more useful fighter&crafter chars
- it requires a good piece of hard work and may not be easy